Switch expression on "this" causes "Syntax node is not within syntax tree" ArgumentExpression in ProjectionExpressionGenerator

[Xriuk]

I am working around the limitations of #74 and I have code like this, which is working:

[Projectable(UseMemberBody = nameof(MyFuncInternal), AllowBlockBody = true)]
public virtual string? MyFunc() {
	return ...;
}
internal string? MyFuncInternal(){
	if(this is DerivedType1)
		return ((DerivedType1)this).MyFunc();
	else if(this is DerivedType2)
		return ((DerivedType2)this).MyFunc();
	else
		return null;
}

However since Type casting is not supported inside ifs (if(this is DerivedType1 t1) t1...) I have to resort to switch expressions, however this doesn't seem to work I'm just getting a silent message ArgumentExpression "Syntax node is not within syntax tree" in ProjectionExpressionGenerator and not much else, and no source files are generated.

[Projectable(UseMemberBody = nameof(MyFuncInternal))]
public virtual string? MyFunc() {
	return ...;
}
internal string? MyFuncInternal() => this switch {
	DerivedType1 t1 => t1.MyFunc(),
	DerivedType2 t2 => t2.MyFunc(),
	_ => null
};